Once Upon a Time's highly anticipated musical episode is almost here, which means that we're just a few days away from witnessing Emma Swan and Killian Jones say "I do" in a breathtaking wedding ceremony. (Trust us. It's perfect.)

ET had the pleasure of visiting Once Upon a Time's set in Vancouver, Canada, last month during filming of the musical matrimony, and we sat down with stars Jennifer Morrison and Colin O'Donoghue for an intimate and in-depth interview that focused on each and every aspect of their on-screen wedding.

From their "honest" vows, to Emma's "timeless" wedding gown, and their dream honeymoon -- only ET has all the inside scoop straight from the stars of the series! Plus, we've got additional details from executive producers Adam Horowitz and Edward Kitsis, as well as Once Upon a Time's head costume designer Eduardo Castro.

So, shall we get started? Or, as O'Donoghue cleverly put it: who's ready for some "music and dance and some mighty fine romance" at Captain Swan's wedding?

Just a warning that this is the biggest Once Upon a Time article we've ever written, so grab a comfy seat, put your cellphone on silent and get ready to go on an emotional roller coaster of feels. And, as always, please remember to breathe!

1. The Venue: The Once showrunners confessed that they had considered a number of "other places" for Emma and Killian to tie the knot -- yes, even Granny's! -- but in the end, they settled on a brand new Storybrooke location for the ceremony. "Without wanting to spoil the episode, there's a story reason for why it's on the roof," Horowitz revealed. "But there's also something to us that was super romantic about having Storybrooke as the backdrop."

Emma and Killian will tie the knot in front of a dream-worthy sunset and surrounded by their closest friends and family. "It's the place where they've kind of come together," Horowitz continued. "Where their love has grown and where both of them as characters have grown, so seeing the whole town kind of beneath and surrounding them felt like a really cool way to do it."

"I thought it was perfect," Morrison dished. "We just felt, like, what better way to make it feel extra special than to have [the wedding] also be the musical episode?"

"Originally we had an ivory gabardine suit made and, somehow, it did not hit the mark," Castro wrote. "At the very last moment, we threw out the ivory and went for a black velvet Burberry jacket that was far more in keeping with Hook's demeanor."

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Kitsis furthered that he and Horowitz had a very specific vision in mind when it came to Hook's look. "Adam and I both thought that Hook needed to have a tux that reflects his personality, so you can't go from leather to just a basic tux," he said. "We felt like he had to have a little edge to it, so the velvet felt like the Hook version of fancy."

When asked if he feels "suave" in his wedding attire, O'Donoghue was bashful with his response. "I guess so," he chuckled. "I hope it looks OK."

"You look amazing!" Morrison chimed in while brushing a piece of lint off of O'Donoghue's sleeve. "He's been getting a little jealous about all of the attention the dress has been getting, so I'm trying to butter him up a little bit about his velvet jacket."

3. The Dress: Morrison, who could not stop beaming during our interview, praised her "absolutely incredible" relationship with Castro and that from "day one" he has included her in each and every fashion choice for Emma. So, naturally, the blonde beauty was an integral part in creating Emma's wedding "vision," and even O'Donoghue had something to add!

"We had talked about it and Colin did say, 'It should be something very vintage,' and I was like, 'Yeah, I agree!' Something Eddy and Adam and I had always talked about was that everything she wears should feel a little bit timeless," Morrison explained. "So we definitely wanted to stay in the classic range with her for the wedding gown, and we felt like what better than a real fairy tale like Grace Kelly's? She was definitely the inspiration for this."

Castro echoed Morrison's sentiments, writing, "Jennifer and I looked at several designs, and she immediately responded to Grace Kelly's wedding dress -- originally designed by Helen Rose in 1956 nearly 60 years ago! The Grace Kelly gown addressed all the concerns that Jennifer Morrison had, so we decided to replicate it."

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"Originally, the wedding was to be shot outside, therefore considerations of warmth needed to be addressed," Castro added. There was a "time crunch" to complete the intricate Alecon Lace and ivory peau de soie gown and matching silk tulle veil and both were constructed in the Once Upon a Time workrooms over the course of two weeks. "We barely had time to fit the gown once, but it all worked out," he said.

As for Emma's gorgeous headpiece? Castro said that his colleague, Isabel Bloor, only had "a few days" to construct it, but it immediately became Morrison's favorite part of the ensemble. "I want to keep this headpiece thing!" the actress declared. "I think it's so spectacular."

4. The Rings: As we were interviewing the on-screen couple, we could not help noticing the massive sparkler on Morrison's finger, which was freshly accompanied by a unique, slightly mismatched wedding band.

"Mmmhmm," O'Donoghue confirmed. "I picked the engagement ring and then they showed me this [wedding band] and I was like, 'Yeah, that'll do.'" To which Morrison added, "They're very inclusive with us around here. It's really nice."

Kitsis and Horowitz explained that they have always encouraged the actors to "take ownership of their characters," and allowing them to select things like the right gowns or props is a natural extension of that. "I think our props department is awesome and I'm sure that they had some great rings," Horowitz said. "Nobody knows the character of Hook better than Colin, so of course he'd be the one to figure out what it should be."

5. The Vows: We're not going to get into the specifics of the vows because we want you all to experience the same, tear-filled awe that we witnessed on set. "The goal with the vows was to have the characters speak sincerely from the heart to each other, and we hope that comes across," Horowitz said.

For the actors, both Morrison and O'Donoghue admitted that Emma and Killian's nuptials are the perfect blend of simplicity and heart.

"I can't speak for Colin, but when I read this script, I loved the whole script," Morrison said. "I felt like just in every single page of it, I was smiling and happy. And not just as someone on the show, but as someone who is a fan -- I just loved it. I was just so happy, and part of what I liked so much about the vows was how simple and honest and direct they are."

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"They weren’t over the top and they're not convoluted in any way," she continued. "I think Hook and Emma are two people who are very direct and they know each other so well at this point. And the fact that the writers made sure that they knew exactly what they needed and wanted to hear in that moment was very, very cool to me."

"Yeah, I felt the same way," O'Donoghue agreed with his co-star. "I was glad that it wasn't reams and reams of lovey-dovey stuff just for the sake of it. It was, as you said, very direct, to the point. I liked the fact that Hook doesn't shy away from the fact that he wasn't great at the start and he just wanted revenge. He just cuts to the chase and says Emma is the reason that he believed that he could love again. She sort of showed him what it was to be in love, so that's what I liked about it."

"It's been so fun! I mean, I feel like I just keep repeating myself. It's just so fun, it's just so fun! You're going to have a whole article of Jennifer said, 'It's just so fun!' over and over again," she exclaimed. "We got to go to the recording studio, we got to work with a great voice coach and, for Emma, the music came from a very organic place. It wasn’t a fantasy sequence or Fairy-Tale Land where it would make sense, but it's just been fun!"

O'Donoghue added that it was great to be able to work with the composers of the musical episode, Alan Zachary and Michael Weiner. "I had never sang in a way where you had to be so expressive and tell the story on top of trying to get the melody out," he explained. "What's great is that the songs all feel like they've been around for forever as part of this sort of Disney world. They really incorporated these brand new songs so well into the story of Once Upon a Time and I think that it's fantastic."

As for Captain Swan's first dance as husband and wife? Prepare to be blown away by their smooth moves. "Yes, we get to dance!" Morrison said. "I mean, I wish I got to dance more. I grew up dancing, so I was wishing that there was more dancing to it."

"I didn’t grow up dancing. I guess I'm just a natural," O'Donoghue said with a laugh.

"He is a natural," Morrison confirmed, "but we also have to deal with the fact that he only has one hand!" O'Donoghue added that learning the choreography has been a bit of a "complicated" process when it comes to the "lifts and stuff," but the two actors are used to the one-handed challenges.

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"You have to move the dance balance around differently and, obviously, we don’t want to, like, have any injuries with the hook. We've gotten really good at working around that hook though," Morrison explained with a giggle. "Wait -- That sounded wrong. I didn’t mean it the way that sounded!"

7. The Honeymoon: Once again, we're not going to spoil the episode's events for you, but when the musical hour ends, and we prepare for "The Final Battle" ahead, it's clear that newlywed bliss may not immediately be in the cards for our couple.

So what do the actors think Emma and Killian's "dream honeymoon" would be? "Five minutes alone probably," O'Donoghue chuckled.

"Yeah, exactly!" Morrison smiled. "Just somewhere with a door locked. I think just a couple bottles of wine and some french fries and a bath, maybe?"

"Oh really, what else?" O'Donoghue pressed.

"I don’t know!" she answered playfully. "I just feel like it should be really relaxing because their lives are very stressful because they're always trying to save people and I feel like a romantic bath might be nice."

"Well, there you go!" O'Donoghue said as he and Morrison burst into laughter.

Once Upon a Time's musical episode, "A Song in Your Heart" airs Sunday, May 7 at 8 p.m. ET/PT on ABC.

How you feeling, Oncers? Tweet your magical thoughts to @LeanneAguilera on Twitter and keep it locked to ETonline for the rest of the week for exclusive interviews with stars Ginnifer Goodwin, Josh Dallas and Lana Parrilla!